Liquid-cooled resistor devices known from the prior art can be employed in a wide variety of applications, including regenerative braking of devices using an inverter-driven electric motor which can also function as a generator.
DE 3933956 discloses a liquid-cooled resistor device for use in electric vehicles, with a flat resistor mounted between two liquid-cooled, electrically insulated blocks. The resistor is kept in place simply by rigid connection between the two blocks. GB2478547 discloses a liquid-cooled brake resistor device for use in electric vehicles, with a flat resistor is disposed between a liquid-cooled, electrically insulated block and a blocking plate or a further liquid-cooled block. The resistor is kept in place by rigid connection between the block and the blocking plate, or between the two blocks, as well as by expansion guide means at last partially surrounding the resistor to confine expansion in its main plane.
One of the drawbacks of the devices of the prior art is that the thermal contact resistance at the resistor-block or resistor-insulation layer interface limits the efficiency and efficacy of the heat transfer. Moreover, the low heat capacity of the block relative to the cooling liquid limits the overall rate of heat dissipation from the resistor.
Further, for use of the devices for braking inverter-driven electric motors, relatively large resistors and liquid-cooled blocks are required in order to manage the high energy dissipation requirements involved, which can in practice render the devices bulky and heavy.